In vehicles, parameter measurement and display systems such as fuel gauge systems may be very nonlinear. This nonlinearity can be caused by several factors, including nonlinearity in the parameter measurement device, such as the sender, irregularity in the shape of the parameter vessel, such as the fuel tank, and nonlinearity in the display device itself, such as the analog gauge or digital display. All of these factors may add up to a total system nonlinearity.
The result of this nonlinearity may be noticed by many vehicle operators during a period of driving when, for example, the fuel gauge takes a long time go from "full" to "3/4 full," but appears to go from "3/4 full" to "empty" faster.
A known method of compensating for system nonlinearities is to use a ROM (or equivalent) look-up table between system circuitry and the display device. The ROM look-up table is addressed by a digital signal from the measurement circuitry representative of the parameter measurement. The ROM contains data, at that address, which drives the display device to an accurate reading of the parameter measurement. The relation between the ROM input address and output data may correspond to points along a curve that represents the system nonlinearity, so that, as a result, the display is driven linearly.
Look-up tables require a large amount of memory, which in turn requires a large amount of silicon area and may be relatively expensive. A major benefit of look-up tables is that they can be programmed, meaning that the only adaptation necessary for different systems with different nonlinearities is re-programming of the data in the memory. What is desired is circuitry to compensate for system nonlinearities, that maintains the adaptability of look-up tables but does not require the silicon area or the expense.